docs: Link to new docs site

I've copied (and slightly cleaned up) all the existing docs
into a new dedicated git repository in

https://bootc-org.gitlab.io/documentation/

docs/builds.md

@@ -2,7 +2,14 @@
 nav_order: 3
 ---
 
-# Configuring systems via container builds
+# This document has moved
+
+See <https://bootc-org.gitlab.io/documentation/>
+
+---
+---
+
+## Configuring systems via container builds
 
 A key part of the idea of this project is that every tool and technique
 one knows for building application container images should apply

docs/install.md

@@ -2,7 +2,14 @@
 nav_order: 2
 ---
 
-# Trying out development builds
+# This document has moved
+
+See <https://bootc-org.gitlab.io/documentation/>
+
+---
+---
+
+## Trying out development builds
 
 Before you build a [derived container image](https://gitlab.com/bootc-org/examples),
 you may want to just get a feel for the system, try out `bootc`, etc.  The bootable

docs/related.md

@@ -2,7 +2,14 @@
 nav_order: 4
 ---
 
-# Relationship with other projects
+# This document has moved
+
+See <https://bootc-org.gitlab.io/documentation/>
+
+---
+---
+
+## Relationship with other projects
 
 ## Fedora CoreOS
 

docs/usage.md

@@ -2,7 +2,14 @@
 nav_order: 3
 ---
 
-# Operating system content and usage
+# This document has moved
+
+See <https://bootc-org.gitlab.io/documentation/>
+
+---
+---
+
+## Operating system content and usage
 
 ## Configuring systemd units